1. Technical Field
An aspect of the present invention relates to an image forming apparatus having a nip-relaxing mechanism, which can clear or relax a nipping condition in a fixing unit in cooperation of an opening motion of a cover of a chassis.
2. Related Art
An image forming apparatus to form an image in toner in an electrophotographic method is often provided with a fixing unit, which fixes the toner image transferred onto a recording sheet thereat by, for example, pressure and heat. The fixing unit includes a heating member (e.g., a heat roller) and a pressing member (e.g., a pressure roller), which are arranged to be in close contact with each other and in opposing positions from each other to nip the recording sheet there-between. When the recording sheet passes through the nipped section between the heating member and the pressing member, the image on the recording sheet is fixed thereat by the pressure and the heat.
Whilst the recording sheet passes through the narrow nipping section, in which the heating member and the pressing member are in close contact with each other, the recording sheet may jam in the section between the heating member and the pressing member in various reasons. When the jammed sheet is removed, therefore, the heating member and the pressing member need to be separated from each other in order to release the sheet. For easier removal of the jammed sheet, an image forming apparatus may be equipped with a mechanism to separate the heating member and the pressing member from each other in cooperation with an opening motion of a cover of the image forming apparatus (see FIG. 13).
The image forming apparatus shown in FIG. 13 is provided with a nip-relaxing member 210, which is connected to the pressing member in the fixing unit, and a connector rod 220, which connects the nip-relaxing member 210 to the top cover 220. When the top cover 200 is opened and closed, the nip-relaxing member 210 is shifted upward and downward in cooperation with the top cover 200 to switch a nipping condition and nip-relaxed condition in the fixing unit. The nip-relaxing member 210 is formed to have a groove 211, in which a shaft 212 in the connector rod 220 is slidably movable.
When the top cover 200 is in the open position, as indicated by a dotted line in FIG. 13, the top cover 200 uplifts the connector rod 220 whilst the connector rod 220 rotates about the shaft 212. Accordingly, the nip-relaxing member 210 is shifted upwardly to clear the nipping condition in the fixing unit. When the top cover 200 is in the closed position, as indicated by a solid line in FIG. 13, the connector rod 220 is rotated about the shaft 212 downwardly. Accordingly, the nip-relaxing member 210 is lowered to place the fixing unit in the nipping condition.